A Comparison of Optical and Electrophysiological Methods for Recording Retinal Ganglion Cells during Electrical Stimulation

Purpose/Aim: To compare the efficacy of optical techniques with electrophysiological recordings for mapping retinal activity in response to electrical stimulation.Materials and Methods: Whole cell patch clamp, Ca2+ imaging (Fluo-4-AM), and Na+ imaging (CoroNa Green-AM) techniques were used to detect responses of neurons from mouse and salamander retina to electrical stimulation.Results: Synaptic currents were observed in ≥23% of retinal ganglion cells (RGCs), indicating presynaptic Ca2+ increases in the inner plexiform layer (IPL). Modest depolarization with 20–30 mM K+ consistently evoked Ca2+ responses measured with Fluo4, but Ca2+ responses were almost never evoked by epiretinal stimulation. In salamander retina, responses were seen in the inner nuclear layer (INL) and IPL. In mouse retina, responses were also sometimes seen in the outer pexiform layer (OPL). OPL responses showed a longer latency than IPL responses, suggesting that outer retinal circuits do not trigger synaptic responses of RGCs. Simul...